Russian Prime Minister Vladimir Putin has acknowledged that he could fail to win an outright victory in the country's March presidential election and face a run-off vote.

Speaking at a meeting with election monitors on Wednesday, Russian news reports quoted Putin as saying he is prepared for such an outcome. But he also warned of the possible dangers of a second round, saying it could lead to political instability.

"As you know, our system allows for a second round, it will depend on the will and the expression of citizens," he said. "It makes sense that I would not have offered my candidacy if I wasn't counting on victory. I also understand and you too understand that a second round would inevitably bring a continuation of a tense fight and obviously political destabilization but there's nothing to fear in this, I'm prepared for it and, if necessary, I will fight the second round.''

Putin, who is seeking a historic third term after his four years as prime minister, has never before needed a run-off, winning his two previous presidential terms in the first round.

But his candidacy is now being challenged by rising popular protests questioning the legitimacy of his 12-year rule and demanding political reforms, fair elections and an end to corruption.

The prime minister's comments come ahead of a massive anti-Putin rally planned for Saturday - one month before the March 4 presidential election.

Putin announced in September his bid to reclaim the presidency and plans to appoint his chosen successor, current President Dmitry Medvedev, as prime minister. The proposed job swap has angered many Russians, and Putin's popularity has since been in decline.

If Putin regains the presidency, the 59-year-old leader could serve two more six-year terms and remain in power until 2024. He was first elected president in 2000 and held that post until 2008 when he assumed the post of prime minister due to term limits.